Ulwazi oluyisisekelo lwe-MOSFET lokuqala kanye nesicelo

Mayelana nokuthi kungani imodi yokunciphisaAma-MOSFETazisetshenziswa, akunconywa ukuthi ufike phansi.

Kulawa ma-MOSFET amabili emodi yokuthuthukisa, i-NMOS isetshenziswa kakhulu. Isizathu siwukuthi i-on-resistance incane futhi kulula ukuyikhiqiza. Ngakho-ke, i-NMOS ngokuvamile isetshenziswa ekushintsheni ukunikezwa kwamandla kanye nezinhlelo zokusebenza zokushayela imoto. Esingeniso esilandelayo, i-NMOS isetshenziswa kakhulu.

Kukhona amandla e-parasitic phakathi kwezikhonkwane ezintathu ze-MOSFET. Lokhu akukhona esikudingayo, kodwa kubangelwa ukulinganiselwa kwenqubo yokukhiqiza. Ukuba khona kwe-parasitic capacitance kwenza kube nzima kakhulu lapho uklama noma ukhetha i-drive circuit, kodwa ayikho indlela yokuyigwema. Sizokwethula ngokuningiliziwe ngokuhamba kwesikhathi.

Kukhona i-diode ye-parasitic phakathi kwe-drain kanye nomthombo. Lokhu kubizwa ngokuthi i-diode yomzimba. Le diode ibaluleke kakhulu lapho ushayela imithwalo ye-inductive (njengamamotho). Ngendlela, i-diode yomzimba ikhona kuphela ku-MOSFET eyodwa futhi ngokuvamile ayitholakali ngaphakathi kwe-chip yesekethe ehlanganisiwe.

2. Izici zokuqhuba ze-MOSFET

Ukuqhuba kusho ukusebenza njengeswishi, okulingana neswishi evaliwe.

Isici se-NMOS ukuthi izovuleka uma i-Vgs inkulu kunevelu ethile. Ilungele ukusetshenziswa lapho umthombo usekelwe (i-low-end drive), inqobo nje uma i-voltage yesango ifinyelela ku-4V noma i-10V.

Izici ze-PMOS ukuthi izovula uma i-Vgs ingaphansi kwenani elithile, elifanele izimo lapho umthombo uxhumeke ku-VCC (high-end drive). Nokho, nakubaI-PMOSingasetshenziswa kalula njengomshayeli wezinga eliphezulu, i-NMOS ivamise ukusetshenziswa kubashayeli abasezingeni eliphezulu ngenxa yokumelana okukhulu, intengo ephezulu, nezinhlobo ezimbalwa zokushintshwa.

3. Ukulahlekelwa kweshubhu ye-MOS

Kungakhathaliseki ukuthi i-NMOS noma i-PMOS, kukhona ukumelana ngemva kokuvulwa, ngakho-ke okwamanje kuzodla amandla kulokhu kumelana. Le ngxenye yamandla asetshenzisiwe ibizwa ngokuthi ukulahleka kwe-conduction. Ukukhetha i-MOSFET enokumelana okuncane kuzonciphisa ukulahleka kokuqhuba. I-MOSFET yanamuhla enamandla aphansi ukumelana ngokuvamile icishe ibe amashumi ama-milliohm, futhi kukhona nama-miliohm ambalwa.

Uma i-MOSFET ivuliwe futhi ivaliwe, akumele iqedwe ngokushesha. I-voltage kuyo yonke i-MOS inenqubo enciphayo, futhi umsinga ogelezayo unenqubo ekhulayo. Ngalesi sikhathi, i-I-MOSFETukulahlekelwa kungumkhiqizo we-voltage kanye ne-current, okubizwa ngokuthi ukulahlekelwa ukushintsha. Ngokuvamile ukushintsha ukulahlekelwa kukhulu kakhulu kunokulahlekelwa kwe-conduction, futhi ngokushesha imvamisa yokushintsha, ukulahlekelwa kukhulu.

Umkhiqizo we-voltage kanye nowamanje ngesikhathi sokuqhuba mkhulu kakhulu, okubangela ukulahlekelwa okukhulu. Ukunciphisa isikhathi sokushintsha kunganciphisa ukulahlekelwa ngesikhathi sokuqhuba ngakunye; ukunciphisa imvamisa yokushintsha kunganciphisa inani lokushintshwa ngesikhathi seyunithi. Zombili izindlela zinganciphisa ukulahlekelwa kokushintsha.

I-waveform uma i-MOSFET ivuliwe. Kungabonakala ukuthi umkhiqizo we-voltage kanye wamanje ngesikhathi sokuqhuba mkhulu kakhulu, futhi ukulahlekelwa okubangelwa nakho kukhulu kakhulu. Ukunciphisa isikhathi sokushintsha kunganciphisa ukulahlekelwa ngesikhathi sokuqhuba ngakunye; ukunciphisa imvamisa yokushintsha kunganciphisa inani lokushintshwa ngesikhathi seyunithi. Zombili izindlela zinganciphisa ukulahlekelwa kokushintsha.

4. Umshayeli we-MOSFET

Uma kuqhathaniswa nama-bipolar transistors, ngokuvamile kukholakala ukuthi akukho okwamanje okudingekayo ukuze uvule i-MOSFET, inqobo nje uma i-voltage ye-GS ingaphezu kwenani elithile. Lokhu kulula ukukwenza, kodwa futhi sidinga isivinini.

Kungabonakala esakhiweni se-MOSFET ukuthi kukhona i-parasitic capacitance phakathi kwe-GS ne-GD, futhi ukushayela kwe-MOSFET empeleni kuyinkokhelo kanye nokukhishwa kwe-capacitor. Ukushaja i-capacitor kudinga i-current, ngoba i-capacitor ingabhekwa njengesifunda esifushane ngesikhathi sokushaja, ngakho-ke i-current instantaneous izoba nkulu kakhulu. Into yokuqala okufanele uyinake lapho ukhetha/uklama umshayeli we-MOSFET inani lamanje le-short-circuit yamanje elinganikeza. .

Okwesibili okufanele kuqashelwe ukuthi i-NMOS, evame ukusetshenziselwa ukushayela okuphezulu, idinga ugesi wesango ukuthi ube mkhulu kunevoltage yomthombo uma ivuliwe. Uma i-MOSFET eshayelwa ohlangothini oluphezulu ivuliwe, i-voltage yomthombo iyafana ne-drain voltage (VCC), ngakho-ke i-voltage yesango ingu-4V noma i-10V enkulu kune-VCC ngalesi sikhathi. Uma ufuna ukuthola i-voltage enkulu kune-VCC ohlelweni olufanayo, udinga i-boost circuit. Abashayeli bezimoto abaningi banamaphampu wokushaja ahlanganisiwe. Kufanele kuqashelwe ukuthi i-capacitor yangaphandle efanele kufanele ikhethwe ukuze kutholwe i-short-circuit current eyanele ukushayela i-MOSFET.

I-4V noma i-10V okukhulunywe ngayo ngenhla amandla kagesi okuvula ama-MOSFET asetshenziswa kakhulu, futhi vele imajini ethile idinga ukuvunyelwa phakathi nomklamo. Futhi lapho i-voltage iphakeme, isivinini sokuqhuba siyashesha futhi sibe sincane ukumelana ne-conductivity. Manje sekunama-MOSFET anama-conduction voltages amancane asetshenziswa emikhakheni ehlukene, kodwa ezinhlelweni zikagesi zezimoto eziyi-12V, ngokuvamile ukuqhutshwa kwe-4V kwanele.

Ngomjikelezo wabashayeli be-MOSFET kanye nokulahlekelwa kwayo, sicela ubhekisele ku-Microchip's AN799 Matching MOSFET Drivers to MOSFETs. Inemininingwane eminingi, ngakho-ke ngeke ngibhale okwengeziwe.

I-MOSFET wuhlobo lwe-FET (enye i-JFET). Ingenziwa ibe yimodi yokuthuthukisa noma imodi yokunciphisa, isiteshi se-P noma isiteshi se-N, ingqikithi yezinhlobo ezi-4. Nokho, i-MOSFET yemodi yokuthuthukisa kuphela esetshenziswayo. kanye nohlobo lokuthuthuka lwe-P-channel MOSFET, ngakho-ke i-NMOS noma i-PMOS ngokuvamile ibhekisela kulezi zinhlobo ezimbili.

5. Isifunda sesicelo se-MOSFET?

Isici esibaluleke kakhulu se-MOSFET izici zayo ezinhle zokushintsha, ngakho-ke isetshenziswa kakhulu kumasekethe adinga ukushintshwa kwe-elekthronikhi, njengokushintshwa kwamandla kagesi namadrayivu ezimoto, kanye nokufiphala kokukhanyisa.

Abashayeli banamuhla be-MOSFET banezidingo ezikhethekile ezimbalwa:

1. Ukusetshenziswa kwamandla kagesi aphansi

Uma usebenzisa ugesi we-5V, uma isakhiwo se-totem pole yendabuko sisetshenziswa ngalesi sikhathi, njengoba i-transistor ibe ine-voltage yehla cishe ngo-0.7V, i-voltage yokugcina yangempela esetshenziswa esangweni ingu-4.3V kuphela. Ngalesi sikhathi, sikhetha amandla esango lokuzisholo

Kukhona ubungozi obuthile lapho usebenzisa i-4.5V MOSFET. Inkinga efanayo iphinde yenzeka uma usebenzisa i-3V noma ezinye izinsiza zamandla aphansi.

2. Ukusebenzisa i-voltage ebanzi

I-voltage yokufaka ayilona inani elingaguquki, izoshintsha ngokuhamba kwesikhathi noma ezinye izici. Lolu shintsho lubangela ugesi wokushayela ohlinzekwa yisekethe ye-PWM ku-MOSFET ukuthi ingazinzi.

Ukuze kwenziwe ama-MOSFET aphephe ngaphansi kwamandla kagesi aphezulu, ama-MOSFET amaningi anezilawuli zamandla kagesi ezakhelwe ngaphakathi ukuze abeke umkhawulo ngamandla we-voltage yesango. Kulokhu, lapho i-voltage yokushayela enikeziwe idlula i-voltage ye-voltage regulator tube, izodala ukusetshenziswa kwamandla amakhulu amile.

Ngesikhathi esifanayo, uma nje usebenzisa isimiso sokuhlukaniswa kwe-resistor voltage ukunciphisa i-voltage yesango, i-MOSFET izosebenza kahle lapho i-voltage yokufaka iphezulu kakhulu, kodwa lapho i-voltage yokufaka incishisiwe, i-voltage yesango izobe inganele, okubangela ukuqhutshwa okungaphelele, ngaleyo ndlela kwandise ukusetshenziswa kwamandla.

3. Isicelo se-Dual voltage

Kwamanye amasekhethi okulawula, ingxenye enengqondo isebenzisa i-voltage ejwayelekile engu-5V noma engu-3.3V, kuyilapho ingxenye yamandla isebenzisa i-voltage engu-12V noma ngaphezulu. Ama-voltage amabili axhunywe endaweni efanayo.

Lokhu kuphakamisa imfuneko yokusebenzisa isekethe ukuze uhlangothi lwe-low-voltage lukwazi ukulawula ngempumelelo i-MOSFET ohlangothini lwamandla kagesi aphezulu. Ngesikhathi esifanayo, i-MOSFET ohlangothini lwe-high-voltage izophinde ibhekane nezinkinga ezishiwo ku-1 no-2.

Kulezi zimo ezintathu, isakhiwo sesigxobo se-totem asikwazi ukuhlangabezana nezidingo zokukhiphayo, futhi ama-IC amaningi omshayeli we-MOSFET angekho eshalofini abonakala engabandakanyi izakhiwo zokukhawulela ugesi wesango.

Ngakho ngaklama isifunda esivamile ukuze sihlangabezane nalezi zidingo ezintathu.

Umjikelezo womshayeli we-NMOS

Lapha ngizokwenza kuphela ukuhlaziya okulula kwesekethe yomshayeli we-NMOS:

I-Vl ne-Vh amandla aphansi kanye nasezingeni eliphezulu ngokulandelana. Ama-voltages amabili angafana, kodwa i-Vl akufanele idlule i-Vh.

I-Q1 ne-Q2 zakha isigxobo se-totem ehlanekezelwe ukuze kuzuzwe ukuhlukaniswa kuyilapho kuqinisekiswa ukuthi amashubhu omshayeli amabili i-Q3 ne-Q4 awavuli ngesikhathi esisodwa.

I-R2 ne-R3 ihlinzeka ngereferensi kagesi ye-PWM. Ngokushintsha lesi sithenjwa, umjikelezo ungasebenza endaweni lapho i-waveform yesignali ye-PWM ingumqansa uma kuqhathaniswa.

I-Q3 ne-Q4 isetshenziselwa ukunikeza idrayivu yamanje. Uma ivuliwe, i-Q3 ne-Q4 inokwehla kwe-voltage ephansi ye-Vce kuphela ku-Vh ne-GND. Lokhu kwehla kwamandla kagesi kuvame ukuba ngu-0.3V kuphela, okuphansi kakhulu kune-Vce ka-0.7V.

I-R5 kanye ne-R6 yizinqamuleli zempendulo, ezisetshenziselwa ukusampula ugesi wesango. I-voltage eyisampula ikhiqiza impendulo enamandla engemihle ezisekelweni ze-Q1 ne-Q2 ngokusebenzisa i-Q5, ngaleyo ndlela ikhawulela i-voltage yesango enanini elilinganiselwe. Leli nani lingalungiswa ngo-R5 no-R6.

Ekugcineni, i-R1 inikeza umkhawulo wamanje oyisisekelo we-Q3 ne-Q4, futhi i-R4 inikeza umkhawulo wamanje wesango le-MOSFET, okuwumkhawulo weqhwa le-Q3 ne-Q4. Uma kunesidingo, i-acceleration capacitor ingaxhunywa ngokuhambisana no-R4.

Lo mjikelezo unikeza izici ezilandelayo:

1. Sebenzisa i-voltage ye-low-side ne-PWM ukushayela i-MOSFET yohlangothi oluphezulu.

2. Sebenzisa isignali ye-PWM ye-amplitude encane ukushayela i-MOSFET enezidingo zamandla kagesi aphezulu.

3. Umkhawulo ophezulu we-voltage yesango

4. Imikhawulo yamanje yokokufaka nokuphumayo

5. Ngokusebenzisa ama-resistors afanelekile, ukusetshenziswa kwamandla okuphansi kakhulu kungafinyelelwa.

6. Isignali ye-PWM ihlanekezelwe. I-NMOS ayidingi lesi sici futhi ingaxazululwa ngokubeka inverter ngaphambili.

Lapho uklama amadivayisi aphathekayo nemikhiqizo engenantambo, ukuthuthukisa ukusebenza komkhiqizo nokwelula impilo yebhethri yizinkinga ezimbili abaklami okudingeka babhekane nazo. Iziguquli ze-DC-DC zinezinzuzo zokusebenza kahle okuphezulu, umthamo wamanje omkhulu, namandla aphansi athule, okuwenza afaneleke kakhulu ukunika amandla amadivayisi aphathekayo. Njengamanje, izitayela eziyinhloko ekuthuthukisweni kobuchwepheshe bokuklama isiguquli se-DC-DC yilezi: (1) Ubuchwepheshe be-High-frequency: Njengoba imvamisa yokushintsha ikhula, usayizi wesiguquli sokushintsha nawo uyancishiswa, ukuminyana kwamandla nakho kwanda kakhulu, futhi impendulo eguquguqukayo iyathuthukiswa. . Imvamisa yokushintsha yeziguquli zamandla aphansi e-DC-DC izokhuphuka ifike kuzinga le-megahertz. (2) Ubuchwepheshe be-voltage ephuma kancane: Ngokuthuthuka okuqhubekayo kobuchwepheshe bokukhiqiza i-semiconductor, amandla kagesi okusebenza ama-microprocessors kanye nezinto zikagesi eziphathwayo ziya ngokuya phansi naphezulu, okudinga ukuthi iziguquli ze-DC-DC zesikhathi esizayo zinikeze amandla okukhipha amandla aphansi ukuze azivumelanise nama-microprocessors. izidingo zamaphrosesa kanye nezinto zikagesi eziphathwayo.

Ukuthuthukiswa kwalobu buchwepheshe kubeke phambili izidingo eziphakeme zokuklanywa kwamasekhethi e-chip yamandla. Okokuqala, njengoba imvamisa yokushintsha iqhubeka nokwanda, izidingo eziphezulu zibekwe ekusebenzeni kwezinto ezishintshayo. Ngasikhathi sinye, amasekhethi ahambisanayo okushintsha idrayivu kufanele ahlinzekwe ukuze kuqinisekiswe ukuthi izinto ezishintshayo zisebenza ngokujwayelekile ekushintsheni amaza aze afike ku-MHz. Okwesibili, kumadivayisi we-elekthronikhi anamandla ebhethri, i-voltage yokusebenza yesekethe iphansi (kuthatha amabhethri e-lithium njengesibonelo, i-voltage yokusebenza ingu-2.5 ~ 3.6V), ngakho-ke, i-voltage yokusebenza ye-chip yamandla iphansi.

I-MOSFET inokumelana okuphansi kakhulu futhi idla amandla aphansi. I-MOSFET ivamise ukusetshenziswa njengesishintshi samandla kuma-chips e-DC-DC adumile njengamanje. Kodwa-ke, ngenxa yamandla amakhulu e-MOSFET e-parasitic, amandla esango lamashubhu ashintshayo e-NMOS ngokuvamile afika amashumi ama-picofarad. Lokhu kubeka phambili izidingo eziphakeme zokuklama i-DC-DC converter switching tube drive circuit.

Kumiklamo ye-ULSI ene-voltage ephansi, kunezinhlobonhlobo zamasekhethi anengqondo e-CMOS kanye ne-BiCMOS asebenzisa izakhiwo zokuthuthukisa i-bootstrap kanye namasekhethi okushayela njengemithwalo emikhulu ye-capacitive. Lawa masekhethi angasebenza ngokujwayelekile nge-voltage yokuphakelwa kwamandla engaphansi kuka-1V, futhi angasebenza ngemvamisa yamashumi ama-megahertz noma amakhulu ama-megahertz anamandla okulayisha angu-1 ukuya ku-2pF. Lesi sihloko sisebenzisa i-bootstrap boost circuit ukuze idizayine isekethe yedrayivu enamandla amakhulu okulayisha amandla afanele i-voltage ephansi, i-high switching frequency boost DC-DC converters. Isekhethi yakhelwe ngokusekelwe kunqubo ye-Samsung AHP615 BiCMOS futhi yaqinisekiswa ngokulingisa kwe-Hspice. Lapho i-voltage yokuhlinzeka ingu-1.5V futhi amandla okulayisha angu-60pF, imvamisa yokusebenza ingafinyelela ngaphezu kuka-5MHz.

Izici zokushintsha ze-MOSFET

1. Izici ezimile

Njengento eshintshayo, i-MOSFET futhi isebenza ezifundeni ezimbili: icishiwe noma ivuliwe. Njengoba i-MOSFET iyingxenye elawulwa yi-voltage, isimo sayo sokusebenza sinqunywa ngokuyinhloko i-voltage yesango lomthombo we-uGS.

Izici zokusebenza zimi kanje:

※ uGS＜i-voltage evulayo UT: I-MOSFET isebenza endaweni enqamuliwe, i-iDS yamanje yomthombo wamanzi ngokuyisisekelo ingu-0, i-voltage ephumayo engu-uDS≈UDD, futhi i-MOSFET isesimweni "sokucisha".

※ uGS>Vula i-voltage UT: I-MOSFET isebenza endaweni yokuqhuba, i-drain-source yamanje iDS=UDD/(RD+rDS). Phakathi kwazo, i-rDS ukumelana ne-drain-source uma i-MOSFET ivuliwe. I-voltage ephumayo UDS=UDD?rDS/(RD+rDS), uma i-rDS＜＜RD, uDS≈0V, i-MOSFET isesimweni "sokuvuliwe".

2. Izici ezinamandla

I-MOSFET futhi inenqubo yoshintsho lapho ishintsha phakathi kwezifunda zokuvula nokuvala, kodwa izici zayo eziguquguqukayo zincike kakhulu esikhathini esidingekayo sokushaja nokukhipha amandla alahlekile ahlobene nesekhethi, kanye nokuqoqwa kweshaja nokukhipha lapho ishubhu ngokwalo livuliwe futhi livaliwe. Isikhathi sokwelashwa sincane kakhulu.

Lapho i-voltage i-ui yokufaka ishintsha isuka phezulu iye phansi futhi i-MOSFET ishintsha isuka kusimo iye endaweni evaliwe, amandla kagesi e-UDD ashaja amandla adukayo CL nge-RD, nesikhathi sokushaja njalo τ1=RDCL. Ngakho-ke, i-voltage ephumayo engu-uo idinga ukudlula ekubambezelekeni okuthile ngaphambi kokushintsha ukusuka ezingeni eliphansi ukuya ezingeni eliphezulu; lapho i-voltage ye-ui yokufaka ishintsha isuka phansi iye phezulu futhi i-MOSFET ishintsha ukusuka kusimo esivaliwe ukuya kusimo, inkokhiso kumandla adukile we-CL idlula ku-rDS Ukukhipha kwenzeka ngesikhathi sokukhipha njalo τ2≈rDSCL. Kungabonakala ukuthi i-voltage ephumayo i-Uo nayo idinga ukubambezeleka okuthile ngaphambi kokuthi ishintshele ezingeni eliphansi. Kodwa ngenxa yokuthi i-rDS incane kakhulu kune-RD, isikhathi sokuguqulwa ukusuka ekunqanyulweni ukuya ekuqhubeni sifushane kunesikhathi sokuguqulwa ukusuka ekuqhubeni kuya ekunqanyulweni.

Njengoba i-rDS yokumelana nomthombo we-drain ye-MOSFET uma ivuliwe inkulu kakhulu kune-rCES yokumelana nokugcwala kwe-transistor, futhi i-RD yokumelana nokudonsa kwangaphandle nayo inkulu kune-RC yokumelana nomqoqi we-transistor, isikhathi sokushaja nokukhipha. ye-MOSFET yinde, okwenza i-MOSFET Ijubane lokushintsha liphansi kunele-transistor. Kodwa-ke, kumasekethe e-CMOS, njengoba isekethe yokushaja kanye nesekethe yokushaja yomibili isekethe elimelana kancane, izinqubo zokushaja nokukhipha ziyashesha kakhulu, okuholela ekushintsheni kwesivinini esikhulu sesekethe ye-CMOS.